There is a significant cost to compliance, even if you do it right from the very beginning (assuming it's even possible for GDPR right now), and for a lot of startups it's not worth it to spend time on that because they'll most likely be dead for unrelated reasons before they get any significant amount of GDPR clients.
It makes more sense to spend the effort on not dying instead of chasing incremental gains in markets with complicated regulatory requirements, unless dealing with those is explicitly your business proposition.
Because adopting the lowest common denominator (GDPR etc.) won't let you grow as quickly, and you might not need the EU market to reach your personal and business goals, or your point of exit.
It might make more sense to split into a EU division once you can really afford it and are established in your main market. I think that this will happen, many will see the EU market just as feature and option to scale an already established business, even companies within the EU. They might start in the US first, and block EU access.
For example, things like the company actively seeking out clients in EU countries, or offering the service in EU countries' languages, make it more likely that EU will consider the company to be subject to GDPR even if it has no presence in the EU.
It seems to me that EU is overstepping their jurisdiction here, but I really don't know how international law works.
An EU citizen buying a product in the US, while in the US, doesn’t pay EU VAT on that product. So it follows that they also wouldn’t be “protected” by European law, despite the color of their passport. US citizens aren’t protected by HIPAA when getting medical care in Britain or France.
Further irony is that many Europeans complain about US “imperialism” in areas such as foreign policy and intellectual property, yet get positively ecstatic over the idea of the EU claiming jurisdiction over companies or users that aren’t in the EU.
Being an EU citizen in the United States using an American product doesn’t make that American product subject to EU law — it doesn’t matter how bad people want to believe that is so.
When in a country, you are subject to that countries laws; you don’t get to bring your home country’s laws with you — except under treaty agreements.